Northern Trail Outfitters uses a custom object Invoice to collect customer payment information from an external billing system. The Billing System field needs to be filled in on every Invoice…

Making a field universally required ensures that users must enter a value into that field whenever they create or edit a record, preventing records from being saved without the necessary information. This enforces data entry at the database level across all record types and page layouts.

An approval process is used to manage how records are approved in Salesforce, not to enforce data entry for a specific field.

Requiring a field on a record type only makes it required on page layouts associated with that record type, and it can be bypassed if the field is not on the layout or if a record type is not used.

Process Builder can automate actions, but it's used to *set* field values or perform other actions, not to *enforce* user input as a requirement for saving the record.